Composition for forming hard coating layer, method of preparing hard coating film and hard coating film prepared by using the same

Abstract

Provided is a composition for forming a hard coating layer, which includes an epoxy siloxane resin, a crosslinking agent including a compound having an alicyclic epoxy group, a thermal initiator including a compound represented by Chemical Formula 2, and a photoinitiator to decrease curls and increase hardness of the hard coating film.

What is claimed is: 
     
       1. A composition for forming a hard coating layer, the composition consisting of: an epoxy siloxane resin, a crosslinking agent including a compound having an alicyclic epoxy group, a thermal initiator including a compound represented by the following Chemical Formula 2, a photoinitiator, and optionally at least one additive selected from the group consisting of a thermal curing agent, a solvent, an inorganic filler, a lubricant, an antioxidant, a UV absorber, a photostabilizer, a thermal polymerization inhibitor, a leveling agent, a surfactant and an antifouling agent, wherein the lubricant is at least one selected from the group consisting of wax, fluorine-based resin, and mixtures thereof: 
       
         
           
           
               
               
           
         
         wherein R 3  is hydrogen, an alkoxycarbonyl group having 1 to 4 carbon atoms, an alkylcarbonyl group having 1 to 4 carbon atoms, or an arylcarbonyl group having 6 to 14 carbon atoms, R 4  is independently of each other hydrogen, halogen, or an alkyl group having 1 to 4 carbon atoms, n is 1 to 4, R 5  is an alkyl group having 1 to 4 carbon atoms or an aralkyl group having 7 to 15 carbon atoms which may be substituted by an alkyl group having 1 to 4 carbon atoms, R 6  is an alkyl group having 1 to 4 carbon atoms, and X is SbF 6 , PF 6 , AsF 6 , BF 4 , CF 3 SO 3 , N(CF 3 SO 2 ) 2 , or N(C 6 F 5 ) 4 . 
       
     
     
       2. The composition for forming a hard coating layer of  claim 1 , wherein the epoxy siloxane resin has a weight average molecular weight of 1,000 to 20,000. 
     
     
       3. The composition for forming a hard coating layer of  claim 1 , wherein the compound having an alicyclic epoxy group is represented by the following Chemical Formula 1: 
       
         
           
           
               
               
           
         
         wherein R 1  and R 2  are independently of each other a linear or branched alkyl group having 1 to 5 carbon atoms, and X is a direct bond; a carbonyl group; a carbonate group; an ether group; a thioether group; an ester group; an amide group; a linear or branched alkylene group, alkylidene group, or alkoxylene group having 1 to 18 carbon atoms; a cycloalkylene group or cycloalkylidene group having 1 to 6 carbon atoms; or a connecting group thereof. 
       
     
     
       4. A preparation method of a hard coating film, the method comprising:
 applying the composition of  claim 1  on a substrate; 
 irradiating the applied composition with ultraviolet rays; and 
 thermally curing the composition irradiated with ultraviolet rays to form a cured hard coating layer. 
 
     
     
       5. The preparation method of a hard coating film of  claim 4 , wherein the epoxy siloxane resin has a weight average molecular weight of 1,000 to 20,000. 
     
     
       6. The preparation method of a hard coating film of  claim 4 , wherein the compound having an alicyclic epoxy group is represented by the following Chemical Formula 1: 
       
         
           
           
               
               
           
         
         wherein R 1  and R 2  are independently of each other a linear or branched alkyl group having 1 to 5 carbon atoms, and X is a direct bond; a carbonyl group; a carbonate group; an ether group; a thioether group; an ester group; an amide group; a linear or branched alkylene group, alkylidene group, or alkoxylene group having 1 to 18 carbon atoms; a cycloalkylene group or cycloalkylidene group having 1 to 6 carbon atoms; or a connecting group thereof. 
       
     
     
       7. The preparation method of a hard coating film of  claim 4 , wherein the thermally curing is carried out at a temperature of 100 to 200° C. for 5 to 20 minutes. 
     
     
       8. The preparation method of a hard coating film of  claim 4 , further comprising: pretreating the composition by heating before the ultraviolet irradiation. 
     
     
       9. The preparation method of a hard coating film of  claim 8 , wherein the pretreating is carried out at lower temperature than the thermal curing temperature. 
     
     
       10. The preparation method of a hard coating film of  claim 4 , further comprising:
 further applying the composition to a surface of the substrate on which the cured hard coating layer is not formed; and 
 ultraviolet-curing the further applied composition to form a photocured hard coating layer. 
 
     
     
       11. The preparation method of a hard coating film of  claim 10 , wherein a thickness ratio of the cured hard coating layer to the photocured hard coating layer is 1.1:1 to 8:1. 
     
     
       12. A hard coating film comprising:
 a substrate; and 
 a cured hard coating layer formed by curing the composition of  claim 1  on the substrate. 
 
     
     
       13. The hard coating film of  claim 12 , wherein the compound having an alicyclic epoxy group is represented by the following Chemical Formula 1: 
       
         
           
           
               
               
           
         
         wherein R 1  and R 2  are independently of each other a linear or branched alkyl group having 1 to 5 carbon atoms, and X is a direct bond; a carbonyl group; a carbonate group; an ether group; a thioether group; an ester group; an amide group; a linear or branched alkylene group, alkylidene group, or alkoxylene group having 1 to 18 carbon atoms; a cycloalkylene group or cycloalkylidene group having 1 to 6 carbon atoms; or a connecting group thereof. 
       
     
     
       14. The hard coating film of  claim 12 , further comprising: a photocured hard coating layer formed by photocuring the composition on a surface of the substrate on which the cured hard coating layer is not formed. 
     
     
       15. The hard coating film of  claim 14 , wherein a thickness ratio of the cured hard coating layer to the photocured hard coating layer is 1.1:1 to 8:1. 
     
     
       16. The hard coating film of  claim 12 , wherein the hard coating film has a curl amount of 5 mm or less, in which the curl amount is measured at each vertex of a square sample cut so that the length of each side is 10 cm and each side is inclined at an angle of 45° to an MD direction of the film.